Telephone-exchange supervisory system.



T. G. MARTIN.

TELEPHONE EXCHANGEES UPERVISORY SYSTEM. APPLICATION FILED JAN-3,1910- RENEWED JULY 20.1916. 1,217,477, Patented Feb:'27,1917.'

. '4 SHEETS-SHEET I.

ll 53:)? I.

mumm- Q; Q

wam a E 1W2 T. G. MARTIN.

TELEPHONE EXCHANGE SUPERVISORY SYSTEM. APPLICATION FILED JAN-3.19m. RENEWED JULY 20.1916.

Patented Feb. 27, 1917.

m w L T. G. MARTIN.

TELEPHONE EXCHANGE SUPERVISORY SYSTEM.

APPLICATION FILED JAN-3,1910. RENEWED JULY 20,1916;

Patented Feb. 27', 1917.

\ 4 SHEETS-SHEET 3.

I 0 o o i z we I E M1 02 2 a? @flmzffm,

T. G. MARTIN.

TELEPHONE EXCHANGE SUPERVISORY SYSTEM.

APPLICATION FILED JANS, 1910- RENEWED JULY 20,19l6.

1,217,477. Patented Feb. 27,1917.

4 SHEETS-SHEET 4- I Q I I IMm STATES PATENT OFFICE.

TALBOT/'G-. MARTIN, or cmcaeo, rumors, ASSIGNOR r0 AUTOMATIC ELECTRIC COMPANY, or cHrcAeqILLmoIs, A oonroaa'rron or rumors.

- Specification of Letters Patent. Patented Feb. 2'7, 1917.

Application filed January 8, 1910, Serial No. 536,131. Renewed July 20, 1916. serial No. 110,414.

To all whom may concern! Be it known that I, TALBOT G. MARTIN, a citizen of the United States of America, and

resident of Chicago, Cook county, Illinois,-

have invented a certain new and useful Improvement in Telephone-Exchange Super-' visory Systems, of which the following is a specification.

' My invention relates to telephone, ex-

change systems in general, but more particu-- larl t0 semi-automatic systems of that particu ar character in which the calling connection passes through an operators cord circuit before reaching the automatic switches, and in which means are provided at the said cord circuit for supervising the connection thus established between the two subscribers lines, whereby the operator at i vision is over a metallic 'circuitvwhen the call is from one exchange to another; to provide an arrangement whereby the supe1= vision isover a third conductor when the call is local, the cord circuit for local calls having arelay which is energized over such third conductor of the trunlir leading to the automatic switches; to provide an arrangement-whereby, when the-call is from one ex change to another, the supervisory control for such connection is in part over a third conductor at the called exchange, and partly over the two sides of the trunk leading from one exchange to the other; to provide an arrangement whereby the introduction of suIiic-ient-resistance into; one circuit, when the called subscriber answers, serves to inmatic telephone exchange system in which no operatmg grounds areemployed at the subscribers stations, and in which the auto .matlc switches are, therefore, necessarily controlled over metallic circuitsthat is to say, circuits which include the two sides of a calling line in series.

To the foregoing and other useful ends my invention consists in-matters hereinafter set forth and claimed.

In the accompanying drawings Figures 1, 2 and 3 takentogether, and in the order named, represent a complete circuit connection between a manual substation A (Fig. 1) and an automatic substation A (Fig. 3) of a distant exchange in a system embodying-the principles of my invention.

In Fig. .1 there is showndiagrammatically a manual substation the line conductors of whichare connected to a jack jat the central oflice. At '0 is shown an operators .cord circuit adapted to extendconnection from a subscribers line jack j to a trunk jack .j', to which latter is connected a trunk leading to a distant automatic exchange.

In Fig. 2 is shown diagrammatically a part of the central ofliceequipment of an automatic exchange with which I have elected to illustrate my invention. At C is shown the automatic exchange terminal of a trunk leading from the manual exchange of Fig. 1. At D is shown a first selector switch, and at E a second selector is represented. I

In. Fig. 3 is shown a connector switch F. At A is shown an automatic substation to the line conductors of which is allotted a crease the flow ofcurrent in another circuit includinga relay, andto thereby energize such relay, thus effecting the retirement of the supervisory signal at the cord circuit to indicate to the operator that the called subsoriber has answered; and to provide certain details and combinations and features of improvement whereby these and other objects are all accomplished in a two-wire system. y

By a two-wire system- I mean that well-known type of automatic or semi-autoline switch H. At R is shown a master switch for controlling, a. group of line switches of which the line; switch H is a member. A central oflice ringer generator is shown at I and at M is, represented a ,busy signaling machine. 4 Q

In Fig. 4 is shown a manual substation A belonging to the same exchange as: siibstation A (Fig-1). At 0 is shown an operators cord circuit for extending a con-.

nection from a manual substation to auto matic switchingapparatus in the-same exchange. At D is shown a first selector-and at [1' is represented a jack for receiving callsfIOIIlffiDEUltOIIliItiC substation for a manual substation. "In the drawings sever-albatteries B are shown with one terminal (preferably the positive) grounded. There may,

, drop is adapted to be actuated by. current from the magneto 5 to signal the operator when a connectionis desired. The cord c1r-'- cuit is an improvement upon the usual cord circuit, since means are provided for giving supervision over a .callto an automatic exchange. As here shown, the cord circuit 0 "comprises the usual supervisory relays 11 and 12, each with its accompanying lamp, and a ringing and listening key K. In addition there is provided a key K for connecting the operators calling device with the calling plug 0'. Since the substations here shown are of the local battery type, while the automatic exchange is common battery, the cord circuit is also provided with a repeating boil N." The operators telephone set L is similar to the ordinary operators set, with the additionof acalIin'g device afor controlling the operation of the automatic switching apparatus.

The automatic exchange terminal C of the trunk from the manual exchange is 'provided with the relays 13, 14, 15 and 16 for the purpose of furnishing means whereby the operator may supervise the call over said trunk. r i i "The-'firstselector D is of the general type disclosed in United States Letters Patent No. 815,321, granted: March 13, 1906', to Keith, Erickson andEricksoIi, the circuits being modified somewhat in order to adapt the switch to operatein conjunction with a twi-wire systemthat is, a system in which no ground connectionis employed at the substation. As here shown, the selector D comprises, among other -details,the wipers 30, 31 and 32 carried upon ashaft (not shown), the said shaft having a vertical motion controlled by the vertical magnet 18 and a rotaryymotion controlled by the rotary magnet 19. The selector D is controlled 1 by the operator throughthe medium of the double-wound line relay 17 The side switch, composed of the wipers 33, 34, 35, 36 and 100, is well known and is controlled by the private magnet 21, which latter is in turn, controlled by the private relay 22. The off-normal spring 37 is normally held out of engagement with contact point 39 by the arm 38 which is attached to the switch shaft. As soon, however, as the shaft is raised one step the arm 38 permits the ductors and 61.

spring 37 to engage the contact point 39, thereby supplying battery current to. the released magnet 20. The selector D is provided with the so-called connector releasethat is, the shaft and side switch are restored immediately upon the energization of the release magnet 20 instead of by the deenergization of the release magnet, as shown in said selector-patent. The switch I) is also provided with a bank of contacts which are in position to be engaged by the wipers 30, 31 and 32, and to which are connected trunks leading to second selectors E. The said second selectors E are similar to the first selector D. Theconnector F (Fig. is of the general type disclosed in United States Letters Pat'- ent No.- 815,176, granted March 13, 1906, to Keith, Erickson and Erickson, and, like the selectors D and E, is adapted to operate in conjunction. with a two-wire system. Like the selectors the connector F is "provided with a shaft (not shown) carrying the wipers 40, 41 and'42 and having a vertical and rotary motion controlled by the vertical and rotary magnets 43 and 44. The operation of the connector is controlled through the medium of the double-wound line relay 45.; A double-Wound back-bridge relay 46 is provided through which the called substation is furnished with talking battery current. A-ringer relay 47 is provided .for the purpose of connecting the ringer generator I with the line of the/called substation after 7 the connection therewith has been completed.

them;v

The automatic substation A may be of any suitable or approved type. As here shown, it comprises the usual receiver 48, switch-hook 49, transmitter 50, induction coil 51, impulse springs 52, ringer 53 condenser 54 and impulse wheel 55. By means of the cam arm 56 the switch hook 49 con-' trols the ringing and talking circuits. When the receiver is on the hook the arm 56 holds the spring 57 in engagement with the spring 58, whereby the ringer 53, in series with the condenser 54 is brid ed across the line conhenthereceiver is removed tromthe hook it rises and permits the spring 57 to engage the spring 59, where- .by the transmitter 50, in series with the primary winding of the induction coil 51, is bridged across the line in place of the ringer 53.

The cord circuit 0' (Fig. 4) is similar to the cord circuit 0 ('Fig. 1), except for the addition of the relay 62 whlch is connected to the third conductor of the plug 12. I

A clearer understanding of my invention may be had from an explanation of its operation when employed in establishing'a connection between two substations. It will first be assumed that the manual substation A desires-connection with the substation A of Fig. 3, the number of which will be assumed to be 2220. The subscriber at substation A first turns the crank of the generator 5, whereby the drop 10 at the central oflice is operated to signal the operator. The manner' in whichtsaid drop-is operated is as follows: As soon as the crank is turned the shaft 63 forces the spring 64 out of engagementwith the spring 65 and into engagement with the spring 66, whereby the circuit of the ringer 6 is opened and the armature of the generator 5 is bridged across the line conductors 8 and 9. Further rotation of the crank causes a rotation of the generator armature, generating a current which flowsv over the conductors 8 and 9 and through the drop 10. The winding of the drop 10 being thus energized, the armature 67 is attracted and releases the shutter 68*, which falls down and indicates to the operator that the subscriber at substation A desires to makea call. Upon receiving the signal of thedrop 10 the operator inserts the plug 1) into the jack j and throws thekey K to close the springs 68 and 69 into engagement with the springs 70 and 71, respectively, whereby 'the talking set L is bridged across the cord 0. The operator may then communicate with the calling subscriber, who removes his receiver immediately after operating the generator to signal the operator.' Upon learning that the substation" #2220 is desired the operator-restores the key K, inserts the plug p into the jack 7'', throws the key K and proceeds to call the desired substation in the usual man-' The operation of the key K, when.

ner. thrown over, is to disconnect the repeating coil N" from the trunk, andbridge across it instead the secondary circuit of the operators set L including the; calling device a.

As soonias theplug p is thus inserted into the jack 7' and-thekey K operated,*the line relay 17 of the selector D- is energized over a circuit extending from ground G at the selector through the winding 7 20f the relay 17, side switch wiper'34 (in first position),

conductor 102, contact point 76, armature 77' of the relay 14 to the trunk conductor 74,

thence through'the sleeve conductors of the jack j and plug 3?, springs 78 and 79 of the key K, thence through the impulse springs 80, secondary of induction'coil and receiver of thebperators set L, and through the springs81 and 82 of the key K and tip conductors of the "plug p and the jack to thetriinli conductor 75, thence through the armature 83 and contact 84 of the relay 14, relay 15, conductor 101, side switch wiper 33 and winding 85 of the relay 17 to-the battery lead 86, thence through battery B to ground G. The relay 17, upon energiz ing, shifts the spring 89 out of engagement withthe spring 87 and into engagement with the spring 88, whereupon an energizing circuit is closed from ground G through the springs 89 and 88 and release relay 23 to the battery lead 86, thence through battery 13 to ground G. The relay 23, upon energizing, shifts the spring 91 out of engagement with the spring- 92 and into engagement with thespring 90, and forces the spring 94 into engagement with the spring 93. The shifting of the spring 91 extends a connection from the impulse spring 87 to the vertical magnet 18 preparatory to the reception of impulses. The engagement of the springs 94 and 93 completes a connection from ground Gr through the side switch wiper 3,5'

impulses for the first digit of the desirednumber, and the operator now operates her calling device in the usual manner for that digit. As the impulse wheel of the operators calling device returns to normal position after having been pulled down, the im: pulse springs 80 are separated twice, thereby twice opening the energizing circuit of the linerelay 17 of the selector D and the relay 15. The relays 15 and 17 thus momenopens the circuit of the release relay 23, but

this relay is a slow-acting relay, that is, slow to deehergize,-and the time of separation of springs 89 and 88' is so short that the said relay does not have time to fall back. Thus the only eflect of the operation of the relay -17 is to send two impulses through the verticalmagnet 18 by the engagement of springs 89 and C87. .The vertical magnet 18 thus receives'two impulses over a circuit extend- 87 ,I91- and 90, private magnet relay 22, .vertical magnet 18' and side switch wiper 36 to 7 battery lead 86, and thence through the bat- 1 tery B to ground G. The vertical magnet 18 responds to these two impulses and raises the shaft two steps to carry the shaft wipers ing from ground Gr through springs 89 and to a position opposite the second bank level, in which are situated the terminals of the trunk leading to the second selector E. The private magnet relay 22 (which was included in the circuit through the vertical magnet) is energized by the first impulse, but being a slow-acting relay (like the relay 23) does not have time to de'energize between impulses. Atter all of the impulses for the digit are completed the relay 17 remains in its energized position, thus opening the circuit through the relay 22 and magnet 18, whereupon the relay 22 allows its armature to fall back after a short time. When the private magnet relay 22 energizes, it closes an energizing circuit for the private magnet 21. This circuit extends from ground G through springs 97 and 98 and private magnet 21 to battery lead 86, thence through battery B to ground G. This energizing circuit is maintained as long as impulses are being sent to the vertical magnet 18. After the last impulse'has been delivered to the vertical magnet, the relay 22 deenergizes, as before explained, and opens the energizing circuit of the private magnet 21, which inturn deenergizes and permits the side switch to pass to second position. When the side switch Wiper 36 engages its second-position contact point it completes an energizing circuit through the rotary magnet 19. This energizing circuit extends from ground G through the interrupter springs 99, rotary magnet 19 and side switch wiper 36 to the battery lead 86, and thence through battery B to ground G. The rotary magnet attracts .its armature, which rotates the shaft wipers onto the first set of bank contacts of the second level, to which they were previously raised by the magnet 18, presses down the armature of the private magnet 21, and also opens the circuit of its own magnet at the interrupter springs 99. \Vhen the circuit of the rotary magnet is thus opened its armature falls back, and if the first trunk is.

idle the armature of the private magnet also falls back and allows the'side switch to pass to third position. If, however, the first trunk engaged by the wipers 30, =31 and ,32 is busy on account of having been seized by some other first selector whose bank is multipled with that of the selector D, the privatei Wiper 32 will find the first contact it engages connected to ground through the first occupying switch. In this case, as soon as the shaft wipers are rotated one step, an energizing circuit is completed extending from the grounded contact engaged by the private wiper 32 through the said wiper 32 and side switch Wiper 100 (which is still in second position) toand through the private magnet 21, thence to the battery lead 86 and through battery B to ground G. The private magnet, being thus energized, does not allow its armature to fall back when the rotary magnet deenergizes, but looks the side switch in second position. The rotary magnet will then be energized a second time upon the closure of the interrupter springs 99 and will rotate the shaft wipers a second step. The rotary magnet will continue to rotate the shaft and its wipers step by step until the private wiper 32 finds a nongrounded contact of an idle line, whereupon the private magnet will deenergize and allow the side switchto pass from second to third position. As soon as the side switch wiper 36 leaves its second position the circuit of the rotary magnet 19 ispermanently opened. When the side switch wipers 33 and 31 pass from second to third position the line relay 17 is cut ofit" from the trunk conductors 101 and 102 and allowed to deenergize, but at the same time an energizing circuit is closed through the line relay 2% of the second selector E. This circuit extends from ground Gr through the winding 103, side switch wiper 104, line Wiper 31 of the first selector D, side switch wiper 34 to the trunk conductor 102, thence through the operators talking set and back to the trunk conductor 101, as'traced for the relay 17, and thence through the side switch wiper 33, line wiper shifts spring 107 out of engagement with spring 108 and into engagement with spring 109, which closes an energizing circuit through the release relay 110 in the same manner in which the relay 17 closed the energizing circuit of the relay 23. The energizing circuit for relay 110 extends from ground Gr through springs 107 and 109 and relay 110 to battery lead 86, thence through the battery B to ground G. The closure of contact between springs 111and 112 by the energization of relay 110 maintains an energizing circuit through the relay 23 of selec' tor D, which relay would otherwise be deenergized by the deenergization of relay 17 when the side switch of the first selector passed to third, position. This new circuit through relay 23 extends from ground G through side switch wiper 113, relay springs 112 and 111, private wiper 32, side switch wiper 100 (in third position) to conductor 114. From conductor 114 one branch of this circuit extends through", relay 23 to battery B, While another. branch extends through. side switch wiper 35 to the relay 16, still maintaining that relay shirt-circuited. The closure of springs-111 and 112 of the 'relay 110 also establishes a guarding potential from ground G to the contact upon which the wiper 32 is resting], as previously traced, and thence to the corresponding contact of all the selector banks that are multipled with that of selector D. This guarding potential prevents any other first selectorfrom establishing connection with'the second se-L lector E while it is in use. Theenergization of release relay 110 of the second selector E also shifts spring 115 out of engagement 19 sition to receive impulses for the second I en the operator operates the calling device a for the second digit (2) the line circuit is opened twice and the line relay 24 of the second selector E denergizes twice in the same manner asdid the relay 17 'of the first selector D whenthecalling device was operated for thefirst digit. Each time the relay 24 denergizes, it opens the circuit of the release relay 110 and closes an energizing circuit through the private magnet relay 29 and vertical magnet 25 in series. The

relay 110, being slow-acting, does not de-,.

energize while the impulses are being sent 25 in, but the vertical magnet 25 responds to the two impulses sent to it and operates to raise the shaft Wipers two steps. The circuit over which the vertical magnet is energized. extends from ground G through 0 springs107 and 108, 115 and 117, private magnet relay 29, magnet 25 and side switch wiper 118 to battery lead 86, and thence through battery to ground G; As soon as the shaft is raised the first step, the off- 3 normal spring 120 engages the contact point -1'19,'whereby the'release magnet 27 is connected with the battery B. The slow-acting private magnet relay 29 is energized by the first impulse to thevertical magnet 25 and remains in its operated position until after the last impulse. As soon as the relay 29 energizes,. it closes an energizing circuit through the private magnet 28. This circuit extends from ground G through springs 121 and 122, and through private 5 net cannot be further operated, and in sec;

' ond position ,it closes an energizing circuit through the rotary magnet 26. This circuit extends from ground G through interrupter springs 123, rotary magnet 26 and 0 side switch wiper-118 to battery lead 86,

thence through the battery B to ground- G, The rotary magnet then energizes once, rotates the shaft wipers onto the first contact of the second level and, if these first contacts are idle, causes the side switch to be tripped ouslytraced.

' from to third position. I If, however, the first trunk is busy, the private magnet is energized by, theprivatewiper 124 coming in contact with the guarded private back contact, and the side switch is locked in second position in the same manner aswas explained in connection with first selector D. The rotary magnet then continues 'to operate to advance-the shaft wipers 124,125 and 126 step by. step until the terminal of an idle trunk is reached, when the private magnet 28 is'deenergiz'ed and the side switch passes to third position, thus extending the connection to a connector switch F (Fig. 3).

The movement of side switch wiper 118 from second to third'position opens the energizing circuit of the rotary magnet 26.. As soon as the connection is, extended to the connector F the line relay 45 energizes and closes an energizing circuit for the release relay 127, which in turn energizes and supplies a new holding ground for the relays 110 and 23 of theswitches E and D, as the ground G is cut off by the denergization of relay 24 when. the side switch of the second selector passes from second position. The energizing circuit of the line relay 45 of the connector extends from ground G through wiper 126,- side switch wiper 104, thence to and through the operators talking set L over a circuit previously traced, and back to wind-ing 128, trunk conductor 129, shaft side switch wiper 105, shaft wiper 125,

trunk conductor 130 and through winding- 131 of relay 45 to battery lead 86, and thence through battery B to ground G. The circuit which is closed through the relay 127 by relay45' extends from ground Gr through springs 133 and 134, 135 and 136 and through relay 127 to battery lead 86,

and thence through battery B to ground G. The new holding ground for the release relays 1'10and23 of selectors E and D extends from ground G at the connector through side switch wiper\ 137, springs 138 and 139 of relay-127 to trunk conductor 140, to the private bank contact upon which the private wiper 124 is resting, then through side switch Wiper 140*, from which one branch passes through relay 110' to battery, while another branch passes through side switch wiper 113 (inthird position), and through relay .23 of selector D over a circuit prev-ien the'operators calling device is now operated 'for-thethird digit 2 the line relay 45 of the connector F is deenergized twice, whereupon the spring 133 'momentarily engages the spring 141- twice. Each time the springs 133 and 141 engage, an energizing circuit is closed extending ground G through springs-133 and 141, 142 and 143 (these springs remaining in contact while the impulses are being sent in because the relay 127 is slow-acting),

steps, and by permitting the off-normal spring 146 to engage contact'point 147 extends a connection from release magnet 148 to the spring 209 of release relay 127,. The privatemagnet relay 144, which is included in the energizing circuit of'the vertical mag net, energizes upon the first impulse and closes an energizing circuit through the private magnet 149. This circuit extends from ground G through springs 150 and 151and private magnet 149 to battery lead 86, thence through battery B to ground G. Since the relay 144 is slow-acting this energizing circuit of the private magnet is maintained as long as the impulses are being delivered to the vertical magnet, After the last of these impulses, the relay 144 has time to deenergize and open the circuit through the private magnet 149. The private magnet in turn deenergizes and permits theside switch to pass from first to secondposition.

The side switchwiper 145, in passing from first to second position, transfers the battery connection from the vertical magnet 43 to t the. rotary magnet 44 in order that the rotary magnet 44 may be operated by ,the relay 45 for the last digit. When the calling device is operated for the last digit (0) the relay 45 is denergized ten times. Since the side switch is now in second position, each time the relay 45 deenergizes a circuit is closed extending from ground G through springs 133 and 141, 142 and 143, private magnet relay 144, relay springs 152 and 153, rotary magnet 44, side switch wiper 145 to battery lead 86, thence through battery B to ground G. The rotary magnet 44 thus receives ten impulses and operates to rotate the wipers 40, 41 and 42 onto the contacts of the desired line #2220. The private magnet relay 144 being also included in the energizing circuit of the rotary magnet is energized by the first of thislast series of impulses and again closes the energizing circuit of the private magnet 149. The re= lay 144 does not have time to deenergize until after the last impulse, when it opens the energizing circuit of the private magnet 149. If the called line is idle when the private margnet relay 1'44 deenergizes this .last time, the private magnet also deener- I gizes and permits the side switch "to pass to thirdposition, whereby the connection is extended to the line of the called substation by means of the wipers 155 and 156. If, however, the called line is busy when the connectonF seeks to make connection with it, the private magnet 149 does not deenergize when the relay 144 deenergi'zes, but remains pulled up, looking the switch in second position and causing the calling subscriber to be given the busy signal as ,follows: Whenever a line is busy, either by reason of having made a call-or ofv having been called, there is a guarding ground potential at its privatebank contact at each of the connectors which has access to the said line.

Thus, when the private wiper 42 comes to rest upon the contact of a busy line a circuit is closed from this grounded contact through the wiper 42, conductor 157, springs 159, 158, side switch wiper 160, contact point 161, contact point 162, side switch wiper 155, ringer relay springs 163 and 164,

gizing circuit for the private magnet 149 independent of the relay 144. This circuit extends from the grounded private bank contact to the contact point 162, as previously traced, and thence through the springs 167 and 168 to and through the private magnet 149 f to the battery lead 86, thence through b' ttery B to ground G. Now, when the r lay 144 deenergizes and permits the spring 150 to engage the spring 169 a circuit is closed extending from ground G through the said springs 150 and 169, private magnet springs 170 and 171, and through the relay 172 to the battery lead 86, thence through battery B to ground GL Therelay 172 then energizes and shifts the spring 159 out of engagement with the spring 158 and into engagement with the spring 173, whereby the holding ground of the relay 46 and private mag- 4 net 149 is shifted from the guarded private bank contact to the ground G. The private magnet thus remains energized and the side switch locked in second position until the connector is released, when the movetactjpoint 176,, side switch wiper 156, ringer relay springs 177 and 178, thence overthe heavy conductors through the operators talking set and back through the winding 193 of-the back-bridge relay 46 to the starting point. The primary circuit of the busy machine M extends from ground G through the interrupter 180, winding 232 and battery B back to ground.

Returning now to that stage of the cal ing operation when the connector wipers.

., switch passes to third position, thus completing the connection between calling and called lines. When the 'side switch wiper 160 passes to its third-position contact it establishes a guarding potential at the connector. private bank contacts of the called line to prevent the said line from beingcalled by any other connector. This guarding potential extends from ground G1 through side switch wiper 160, relay springs 159and 158, conductor 157, wiper 42 and bank con- 7 tact 181, and thence to the corresponding contact in the banks of all other. conneglors so from the contact 181 a conductor extends td battery lead 86, thence through the battery B to ground G. The relay 182' is energized when this circuit is closed and operates to disconnect the line switch H from the lines of substation A. When the side switch wiper 145 of the connector reach'es third position a circuit is closed through the ringer relay 47. This circuit extends from ground Gr through interrupter 183, springs 165 and 166, relay 47 and side switch wiper 145 to battery lead 86, thence through the battery B to ground G. Since this circuit includes the interrupter 183 the relay 47 will be energized intermittently. Each time the ringer relay 47 is energized the springs 163 and 177 are forced outof engagement with springs 164 and 178 and into engagement with springs 184 and 185, respectively. By this shifting of the ringer relay springs the connection between the calling and called lines is opened and the ringer generator I is bridged across the called line, thusringing the bell 53 atthe called substation. The bell 53 will thus be rung intermittently until the receiver is removed from the hook. Also when the side switch of the connector passes from second to third position the wiper 137 transfers the holding ground of the release relays of the selectors D and E from ground G to groundG The holding traced. Thisground G also maintains the short-circuit of the relay 16.

After the operator has completed the call the key K is restored, thus cutting oif the operat'ors calling device and. bridging the supervisory relay 12 and windings 186 and 187 of the repeating'coil N across the line instead. The relay 12 is thus included in the energizing circuit of the line relay 45 of the connector F, and consequently a'ttracts its armature 188 onto the contact point 189, completing a circuit through the lamp -190. The relay 12 remains. energized and the lamp 190 continues to glow until the called subscriber answers the call by removing his receiver from the hook. When the called subscriber removes his receiver '1 from the switch hook, in answer, to the call,

the circuit of the ringer 53 is opened by the separation of'the springs 58 and 57, and the primary'talking circuit is bridged across the line instead. As soon as the ringer relay 47 deenergizes, after the receiver is removed from the switch hook, the called substation is provided with talking battery current over a' circuitv extending from ground G through the winding 1-92 of the back-bridge relay 46, ringer relay springs 178 and 177,

side switch wiper 156, shaft wiper 41, line conductor 61, springs 57 and 59, impulsesprings. 52, primary of induction coil 51, transmitter 50, conductor 60, shaft wiper 40, side switch wiper 155, relay springs 163 and. 164, and winding 193 of the back bridge relay 46 to the battery lead 86, thence through battery B to ground G. The relay 46, which is included in this circuit, energizes,

and by separating the springs 165 and 166 opens the circuit of the ringer relay 47 to prevent ringing current from beingthrown on the line. Also, when the relay 46 energizes, the springs 135 and 136 are separated,

thus removing the short-circuit from the resistance 194. The resistance 194 is thus introduced into the holding circuit of the release relays 127,110 and 23. When the resistance 194 thus enters the circuit of the release relays the relay 16 is no longer shortcircuited, but is also included in the circuit of the release relays in multiple with the resistance 194. The relay 16 then receives enough current to attract its armature 195 against the contact point 196. When the armature 195 thus engages the contact point 196 an energizing circuit is closed from ground G through the relay 14 to battery. The relay 14, upon energizing, attracts its armatures 83 and 77 out. of engagement with contact points 84and 76 andinto engagement with contact points 197 and 198, respectively. This operation of the relay 14 disconnects the trunk conductors 75 and 74 from conductors 101 and 1,02 and connects them with the windings of relay 13. The relay 13 thereupon energizes and 40 7 of. the jack j and plug p, armature 204, conbridges the relay 15 directly across the conductors 101 and 102 through the springs 199 and 200, thus maintaining the energizing circuit of the relay 15 and of the line relay of the connector F. The energizing circuit of the relay 13 extends from ground G through the winding 201, contact 197, armature 83, trunk conductor 75, tip springs of jack j and plug 1), winding 186 of the repeating coil N, relay 12, winding 187, rlng springs of plug 1) and jack j, conductor 74, armature 77, contact 198 and winding 202 to battery lead 86, thence through battery B to ground G. Although the relay 13 energizes over this circuit its resistance is so great that enough current does not flow to maintain the supervisory relay 12 in its energized position, but allows the" armature 188 to drop back from the contact point 189. When the armature 188 and contact point, 189 are thus disengaged, the lamp 190 is extinguished, signifying to the operator that the called subscriber has answered the call.

After the subscribers are through conversing the operator is given a disconnect signal as follows: After the subscriber at the manual substation A restores his receiver to the switch hook the crank of the magneto 5 is again rotated. In this. case'the' operation of the magneto 5 applies ringing current to the line in the same manner as when the call was started. In this case, however, since the plug p is in the jack j ringing current passes through the winding 203 of the supervisory relay 11, causing the armatur204 of said relay to be drawn into i engagement with the contact point 205.

The engagement of armature 204 with the contact point 205 closes a circuit extending from ground G" through the sleeve contacts through battery B to ground G. The relay 11 will thus remain energized and the lamp 206 lighted until the plug p is removed from the jack j.

When the called subscriber hangs up his receiver the energizing circuit of the backbridge relay 46 is opened and the resistance conductors 101 and 102, whereupon the supervisoryrelay 12 (Fig. 1) again energizes in series with relays 15 and 45. The energlzatlon of relay 12 again lights the lamp selector 1). (Fig. 2).

local-automatic subscriber the operator in-' 190. The simultaneous glowing of lamps 190 and 206 signifies .to the operator that both subscribers have hung up their receivers and that the, connectionmay be released. The operator then withdraws the plugs 11 and p from their respective jacks and the automatic switches are automatically restored as follows: The removal of plug p from jack 1' destroys the energizing circuit of the relay 15 and of the line relay 45 of the connector F. These two relays consequently deenergize and openv the holding circuit of the release relays .127, 110 and 23 of the switches F, E and D, and these relays de'nergize after a short interval to close the energizing circuits of the release magnet of their respective switches. The energizing circuit of the release magnet 148 of the connector F extends'from ground G through springs 133 and 141, 142 and 209, off-normal springs 146 and 147 and magnet 148 to battery lead 86, thence through battery B to ground G. The release magnet 27 of the second selector E is energized over a circuit extending from ground G through the springs 107 and 108, 115 and 116, magnet27, off-normal springs 119 and 120, to the battery lead 86, and thence through battery B to ground G. The release magnet 20 of the first selector D is energized over a similar circuit. The magnets 148, 27 and 20, uponenergizing. immediately restore the mechanism of their respective switches to normal position. \Vhen the shaft of each switch reaches its normal position the circuit of its release magnet is opened by the separation of the off-normal springs 146 and 147, 120 and 119, 37 and 39. Of course, as soon as the plugs p and p are removed from the jacks 7 and j the supervisory relays 11 and 12 are deenergized and the lamps 206 and 190 extinguished. i

If the manual subscriber wishes to call an automatic subscriber of the same exchange the cord circuit 0 is used. In this case the operator is signaledin the same manner as previously explained. The trunk leading from the jack j to the local first selector D is not provided with a group of relays C as was the trunk leading to the distant exchange, but .the plug p and the jack 7' are each provided with a third conductor, and the cord circuit 0 is provided with a relay 62 which, when the plug 79* is inserted in the jack j, is connected with the selector D in the same manner as is the' relay 16 with the In order to call the serts the plug p into the jack j, throws the key K and operates the calling device a in the usual manner. The operation of the calling device for the first digit eifects the operation of the selector D in the same manner as the selector D was operated for the first digit of the number 2220. It is assumed that from the banks of the selector D trunks lead to connector switches similar nector in the same manner as .when #2220 was called, and the connection is thereby extended to the called line. After the connection has been completed the key K is restored, thus bridging the supervisory relay- 210 across the line in series with two wind- ,ings of the repeating coil N. As soon as, the relay 210 is thus bridged across the line I it. energizes in series with the line relay of the connector, just. as the relay 12 was energized in series with relay 45 in the previous case. When the-relay 210 energizes it completes a circuit through the lamp 211, said circuit extending from ground Gr through armature 212, contact 213, armature 214, contact 215, lamp 211 and tobattery lead 216, thence through battery B to ground G. After theconnection has been completed and before the called subscriber answers, the relay 62 is short-circuited by the ground G at the connector just as was the relay 16. Also, as soon as the called subscriber answers,

the relay 62 and resistance 194 are connected in multiple, just as was the relay 16 and resistance 194 in the former case. The relay 62 thereupon energizes and, by attracting the armature-214 away from the contact 215, opens the circuit of the lamp 211, thus indicating to the operator that the called subscriber has answered. After the conversation is completed the operator is given the disconnect signal in practically the same manner as when the subscriber at substation A called the subscriber at substation A' The actuation of the generator at substation A energizes the relay 217, which causes the lamp 218 to glow just as the relay 11 and lamp 206 were operated at the substation A. When the called subscriber hangs up his receiver the back-bridge relay of the connector deenergizes and again short-circuits the resistance 194. -When the resistance 194 is short-circuited it again causes the relay 62 to be short-circuited also, and the said relay deenergizes. When the relay 62 deenergizes it again closes the circuit of the lamp 211 to:

notify the operator that the called subscriber has hung up his receiver. Upon seeing the simultaneous glowing of the two lamps 211 and 218 the operator removes the plugs and p from their jacks and the release of the automatic switches follows in the manner already explained.

It is understood, of course, that the exchange may be provided with any suitable cord circuit for establishing connection between two manual subscribers, butas my invention is not concerned with such a connection I have shown no such cord circuit.

To provide for calls from automatic subscribers to manual subscribers, jacks 9' are provided which are connected to trunks leading. from the banks of automatic se lector switches in both the local exchange a and the distant exchange. Whenthe autoleading to a jack' 1' As soon as the connection is thus established with jack 7' the callmg substation is, provided with talking battery current over a circuit extending from ground G through winding 219 of relay 220, conductor 221, thence through the calling substation and back over, conductor 222 and through winding 223 of relay 220 to battery lead 2l6,thence through battery B to ground G. The relay 220 energizes upon -the completion of this circuit and operates to close springs 224' and 225 into engagement with springs 226 and 227,

respectively. The engagement of springs 225 and 227. connects ground G with conductor'231 for maintaining the release relay of the automatic selector switch. energized.

"through battery B to ground G. The consequent glowing of lamp 230,1 upon the completion of this circuit, notifies the operator that some one is calling into this jack. The operator then inserts a plug of one of the cords in the jack j inquires'the number of the calling substation and the number desired, and then asks the calling subscriber to hang up his receiver. The hanging up of the receiver at the calling substation breaks the energizing circuit of relay 220, whereupon the said relay de'e'nergizes. The separation of springs 225 and 227.b y the deenergization of relay 220 opens the energizing circuit of the release relay of the selector switch, whereupon the said switch is released in the .usual manner. After ascertaining the number of the calling and desired substations, the operator removes the plug from jack 9' and inserts the plug 7' of cord 0 or plug y' of cord 0 (depend-- ing upon whether the calling substation belongs to the local or to the distant exchange) into thejack of the desired line and operates the ringing key K or K to signal the substation. The operator then inserts the other plug of thecord into a jack j gr 1" (also depending upon the exchange to which the calling substation belongs) and proceeds to call the original calling substation in the usual manner. After the conversation is completed the op- The engagement of springs 224 and 226 .ductors of, the trunk lines.

erator is given the disconnect signal in the manner already explained, and the automatic switches are released upon the removal of the plug, as in the previous cases.

From the foregoing it will be seen that the supervisory control, when the call is tending between the two exchanges. The

called subscriber, in answering, introduces the resistance 194 into one circuit, thereby removing the short-circuit around the relay 16 and increasing the current-flow in this relay sufiiciently to cause it to energize and close the local circuit through the relay 14.

This part of the supervisory control, it will be seen, not exercised over the two sides of the talking circuit, but simply over the third conductorsof the trunks between the relays C and the connector F, which third conductors are also used for releasing purposes. The energizing of the relay 14 serves to bridge the high resistance coils 201 and 202 across the trunk line 7i and 75, and to thereby decrease the current-flow in the relay 12 of the cord circuit 0, which serves to open the circuit of the lamp 190. Thus, as stated, the supervisory control between the two exchanges is exercised over a metallic circuit including the two sides of the trunk line in series. The relay 13 must be in bridge of the said trunk line during conversation, so as to hold the relay 15 in bridge of the trunk circuit to the connector, whereby the operator at the cord circuit 0 may, by withdrawing the plug, release the automatic switches when the conversation is terminated. When the plug is withdrawn the relay 13 is deenergized, and the opening of the bridge in whichthe relay 15 is included serves to de'e'nergize all of the release relays heretofore described, and thus release the switches; When the call is local, as from one subscriber to another in the same exchange, then the arrangement shown in Fig. 4 is used, in which case the supervisory 'control is exercised entirely over the third c'onmy invention.

In this case the r What I claim as my invention is 1. In a telephone system, a connector provided with a side switch having three positions, an operators supervisory relay, a supervisory signal, means for energizingsaid cord circuit, a called line, means for extending connection to said line, a third conductor intermediate the trunk line and the called line, andrelays whereby the control p of such supervisory apparatus by the called subscriber includes circuits that are partly over said third conductor. and partly over the two sides of said trunk line.

3. In a telephone system, means for extending connection to a called line, said means including a cord circuit, a supervisory apparatus therefor, a trunk line, a relay individual to said trunk line,'a circuit forshunting or short-circuiting said relay, a resistance and means for introducing it in said circuit when the called subscriber answers to energize said relay, and means controlled by said relay for placing resistance in series with the trunk line to control the said supervisory apparatus.

4. In a telephone system, a cord circuit, a supervisory apparatus therefor, means including an automatic switch for extending a connection from said cord to a called subscribers line, a trunk line comprising three parallel conductors extending to said switch, and means for controlling said supervisory apparatus over the third conductor to the exclusion of the other two of said trunk line when the called subscriber answers.

5. In a telephone system, a cord circuit,a supervisory relay therefor, a trunk line having a third conductor, a circuit for energizingsaid relay, which circuit includes said third conductor, a circuit for shunting or short-circuiting said relay to prevent the same from energizing, a resistance and means for introducing it in said short-circuit when the called subscriber answers, and a supervisory signal controlled by said relay.

6. In a telephone system, a connector-provided with a local circuit, a resistance in said circuit, a normally closed short-circuit around said resistance, means for opening said short-circuit when the called subscriber answers, and a supervisory signal controlled by the opening of said short-circuit.

7. In a telephone system, a trunk line, condensers therein, an automatic switch for said trunk lir e for extending a connection to the called subscriber, a low resistance normally open bridge across said trunk line between said condensers and automatic switch, a high lid resistance relay controlling said bridge, means controlled by the called subscriber for placing said high resistance relay in bridge of the trunk line at the other side of said condensers, a source of current, included in said last-mentioned bridge, and a relay in said first-mentioned bridge, this last-mentioned relay controlling the said means for bridging the high resistance relay across the trunk line. i

8. In a telephone system, manual and automatic means for establishing a talking circuit between calling and called substations, a manual switchboard operators supervisory signal, a third conductor, means whereby the control of said supervisory signal by the called subscriber is partly over the third conductor and partly over the two sides of th talking circuit in series.

9. In a telephone system, a talking circu1t between calling and called substations, a/ manual switchboard operators supervisory signal, a third conductor extending parallel with the talking circuit at the exchange or called subscriber for first controlling said last-mentioned circuit, and means controlled over this circuit for then controlling the said first-mentioned circuit to control the said signal. I

11.-In a telephone system, a calling manual switchboard subscribers linefa called automatic exchange 'subscribers line, a manual switchboard provided with means'for answering the call, means including one or more switches controllable fromsaid switchboard for completing the connection to the called line, H/SUPGIVISOIY signal at the manual switchboard, a talking circuit including the two lines and the connection between the same, a supervisory circuit for controlling said signal, said circuit including portions of the two sides of the'talking circuit in series, another circuit which excludes all portions of the talking circuit, means in said last-mentioned circuit for controlling the said supervisory circuit, and means responsive to the called subscriber for controlling the said circuit which excludes all portions of the talking circuit to control the said supervisory signal.

circuit for controlling the said signal, said circuit including portions of the two sidesot said talking connection in series, a relay for controlling said circuit, and means responsive to the called subscriber for controlling said relay, said last-mentioned means ineluding a circuit from which all portions of the said talking connection are excluded.

13. In a telephone system, -a manual switchboard provided with a supervisory signal, a metallic line circuit for controlling said signal, a talking circuit which includes the two sides of said line circuit, automatic switches for controlling said talking circuit, means including third conductors extending from one switch to another for releasing the same, and means including said third conductors for controlling said metallic line conductors to control the said signal.

14. In a telephone system, calling andcalled telephone lines, instrumentalities for establishing a combined automatic and manual trunking connection between the two llnes, a supervisory slgnal for the operator who controls the manual portion of the connection, and means including a plurality of circuits by whlch the called subscriber controls said signal, one circuit controlling another, all portions of the said trunking connection being excluded from one circuit, and another of said circuits including a portion of the said connection.

15. In a telephone system, a supervisory signal, a two-wire trunk line, a three-wire trunk line, devices for including said trunk lines in a talking connection between calling and called substations, with the third wire of the .last mentioned trunk line excluded from the path. of the voice-currents, and means whereby the control of said signal is in part over said third wire and in part over both sides of the first-mentioned trunk line.

1 6. In a telephone system, a manual sw1tchboard operators supervisory signal, a two-wire trunk line, a three-wire trunk line, means for including said trunk lines in a talking connection between calling and called substations, with the third wire of the tioned trunk line, the-three-wiretrunk line being located between the two-wire trunk line and the called subscribers line.

17. In a telephone system, means including a trunk line for extending a connection to the called lme, a condenser in each side of said trunk line, a relay connected around one of said condensers, a second relay, normally closed contacts in said connection controlled by said second relay, a third relay controlling the circuit of said second relay, and

means for energizing said third relay when the called subscriber answers to control said first relay.

18. In a telephone system, an operators cord circuit, a supervisory signal therefor, means including a trunk line adapted to be connected With said cord circuit for extending a connection to a called line, means in said trunk line for controlling said supervisory signal, said means including a relay adapted to be energized over said trunk line, a second relay for controlling said relay, and a third relay adapted to be energized upon the response of the called subscriber to render said signal inoperative and to control said first relay.

19. In a telephone system, subscribers lines, means including an operators cord circuit and a trunk line for establishing a connection between two of said lines, a third conductor in said trunk, a supervisory signal, means for applying ground to both ends of said trunk, means for inserting a resist ance in one of said ground connections, and means controlled thereby for controlling said supervisory sigal.

20. lln a telephone system, subscribers lines, means including an operators cord circuit and a trunk line for establishing a connection between two of said lines, a third.

conductor in said trunk, a supervisory signal, means for applying ground to both ends of said trunk, means controlled by the response of the called subscriber for inserting a resistance in one of said ground connections, and

means controlled thereby for controlling said 

